Method and computer program product for generating secure alternative representation for numerical datum

ABSTRACT

A method for generating secure alternative representation for a numerical datum, being performed in a processing system comprising a processing unit coupled to a storage unit, is provide. The method comprises: receiving the numerical datum; providing a plurality of semi-finished conditions; associating each of the semi-finished conditions with one or more secret parameters to form a plurality of secret conditions; for each of the secret conditions: determining whether the numerical datum satisfies the secret condition; outputting a first character as a result element if the numerical datum satisfies the secret condition; and outputting a second character as the result element if the numerical datum does not satisfy the secret condition; and concatenating each result element being output corresponding to the secret conditions as an alternative representation for the numerical datum.

TECHNICAL FIELD

The application relates to a method and a computer product forgenerating secure alternative representation, especially to a method anda computer product for generating secure alternative representation fornumerical datum.

BACKGROUND

Cloud applications are around those who connect themselves to thecyberspace, when search engines have already become inevitable tools andcloud storage services also have been attracting a vast number of usersexperiencing extraordinary mobility, scalability and availability forfree. However, users do pay for these benefits in term of their privacy.

Being aware of possible infringements made by hackers or serviceproviders, users are increasingly demanding their privacy. In order toavoid personal information leakage, data are suggested to be encryptedbefore being stored in one or more corresponding servers in cloud.Nevertheless, encrypted data may make the searching for particular datahard, if not impossible, and thus results in inconvenience duringsearching and/or retrieving data stored in the corresponding server(s).Based on the above considerations, how to provide a secure yeteasy-to-search data retrieval mechanism is one of the subjects ofindustry efforts.

SUMMARY

An embodiment of the present application discloses a method forgenerating secure alternative representation for a numerical datum,being performed in a processing system comprising a processing unitcoupled to a storage unit. The method comprises: receiving, by theprocessing system, the numerical datum; providing, by the processingsystem, a plurality of semi-finished conditions; associating, by theprocessing system, each of the semi-finished conditions with one or moresecret parameters to form a plurality of secret conditions; for each ofthe secret conditions: determining, by the processing system, whetherthe numerical datum satisfies the secret condition; outputting, by theprocessing system, a first character as a result element if thenumerical datum satisfies the secret condition; and outputting, by theprocessing system, a second character as the result element if thenumerical datum does not satisfy the secret condition; andconcatenating, by the processing system, each result element beingoutput corresponding to the secret conditions as an alternativerepresentation for the numerical datum.

Another embodiment of the present application discloses a computerprogram product comprising a non-transitory computer readable mediumhaving a computer readable program stored therein. When the computerreadable program is executed at a processing unit of a processingsystem, causes the processing system to perform steps comprising:receiving a numerical datum; providing a plurality of semi-finishedconditions; associating each of the semi-finished conditions with one ormore secret parameters to form a plurality of secret conditions; foreach of the secret conditions: determining whether the numerical datumsatisfies the secret condition; outputting a first character as a resultelement if the numerical datum satisfies the secret condition; andoutputting a second character as the result element if the numericaldatum does not satisfy the secret condition; and concatenating eachresult element being output corresponding to the secret conditions as analternative representation for the numerical datum.

The above and other aspects of the invention will become betterunderstood with regard to the following detailed description of thepreferred but non-limiting embodiment(s). The following description ismade with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of a processing system according to anembodiment of the present application.

FIG. 2 shows a flowchart of a method for generating secure alternativerepresentation according to an embodiment of the present application.

FIG. 3 shows an example of generating an alternative representation fora numerical datum according to the present application.

FIG. 4 shows another example of generating an alternative representationfor a numerical datum according to the present application.

FIG. 5 shows yet another example of generating an alternativerepresentation for a numerical datum according to the presentapplication.

FIG. 6 shows yet another example of generating an alternativerepresentation for a numerical datum according to the presentapplication.

DETAILED DESCRIPTION

Referring to FIG. 1, FIG. 1 shows a block diagram of a processing systemaccording to an embodiment of the present application. The processingsystem 10 includes one (or more) storage unit 102 and one (or more)processing unit 104. The storage unit 102 is configured to store data,applications, procedures, computer readable instructions or computerreadable programs which are configured for generating alternativerepresentations for numerical data. The processing unit 104 isconfigured to execute the applications, the procedures, the computerreadable instructions or the computer readable programs to perform themethod for generating alternative representation. In some embodiments, acomputer program product comprising a non-transitory computer readablemedium may be employed to store applications, procedures, computerreadable instructions or computer readable programs. When theapplications, the procedures, the computer readable instructions or thecomputer readable programs is/are executed on the processing system 10,it causes the processing system 10 to perform the method for generatingalternative representations.

In the present application, one or more alternative representations canbe generated for a numerical datum which may be a numerical value (e.g.,a real number) or a numerical range (e.g., [a,b] or (a,b), where a and bare real numbers). In an embodiment, the numerical datum may be includedin a document, a table, or a file, for example, stating a financialstatement of a company. The data owner (user) may expect to hide thenumerical datum before storing the numerical datum (or the document,table or file including the numerical datum) into a remote storage spacein a server 90. In this situation, before storing the numerical datuminto a remote storage space in a server 90, the method according to thepresent application is able to generate one or more alternativerepresentations used as a secure index or secure indexes representingthe numerical datum while hiding its actual content. In anotherembodiment, when the data owner (user) needs to identify the previousgenerated secure index or secure indexes stored in the remote storagespace and/or wants to retrieve the associated encrypted numerical datum,an input numerical datum such as a numerical range may be used as aquery, and the method according to the present application may be usedto generate one or more alternative representations used as a securetrapdoor or secure trapdoors to identify the secure index or secureindexes.

For the exemplary purpose, a data retrieval mechanism can be enabled bythe method which generates one or more secure indexes for each ofprivate or confidential objects, such as files, documents and tables,before doing encryption over these objects in user-side; after uploadingthe encrypted object and the associated secure index or secure indexesto a server, one can retrieve wanted encrypted objects from the serverif a matching secure trapdoor could be provided as a clue to identifythe associated secure index(es).

The processing system 10 may be implemented by a cellphone, a personalcomputer, a laptop, a smart phone, a tablet, or any device withcomputation function and a network connection. For example, theprocessing system 10 is able to be connected to a server 90, and sendthe generated alternative representations used as secure indexes to theserver 90 and thus store the alternative representations in the server90. Also, the processing system 10 may send the generated alternativerepresentations used as secure trapdoors to the server 90 to searchdesired index(es) among the secure indexes stored in the server 90.

In the embodiment, since the numerical datum is transformed into analternative representation which is used as a secure index instead ofthe numerical datum to store into the server 90, the server 90 cannotobserve the actual content of the numerical datum from the secure index.Similarly, when searching, since the numerical datum which is used asquery is transformed into an alternative representation which is used asa secure trapdoor instead of the numerical datum, the server 90 cannotobserve the actual content of the numerical datum from the securetrapdoor either.

Referring to FIG. 2, the method in FIG. 2 includes steps S201˜S209. Inthis embodiment, the method shown in FIG. 2 is used for generatingalternative representation which may be used as a secure index. Alsoreferring to FIG. 3 which illustrates an example of generating analternative representation for a numerical datum according to thepresent application.

In step S201, the processing unit 104 receives a numerical datum. Inthis example, the numerical datum is a numerical value, that is, 35. Thenumerical datum may be input by a user or stored in the storage unit 102of the processing system 10.

In step S203, the processing unit 102 provides a plurality ofsemi-finished conditions. In this example, the semi-finished conditionsare “>”, “(,)”, “,]”, “>”, “˜[,)”, “≤”, “˜[,]” and “˜(,)”, where “>”refers to “larger than”, “(,)” refers to “within the range (the upperbound and the lower bound are not included in the range)”, “(,]” refersto “within the range (the lower bound is not included in the range)”,“˜[,)” refers to “not within the range (the upper bound is not includedin the range)”, “≤” refers to “less than or equal to”, “˜[,]” refers to“not within the range”, and “˜(,)” refers to “not within the range (theupper bound and the lower bound are not included in the range)”.

In an embodiment, the semi-finished conditions are selected randomlyfrom a set of semi-finished conditions, which may include semi-finishedconditions such as “>”, “<”, “=”, “≥”, “≤”, “≠”,“(,)”, “[,]”, “(,]”,“[,)”, “˜(,)”, “˜[,]”, “˜(,]”, “˜[,)” and so on.

In step S205, the processing unit 104 associates each of thesemi-finished conditions with one or more secret parameters to form aplurality of secret conditions. In this example, the secret parametersare 89, 12, 42, 8, 67, 22, 57, 91 67, 24, 58, 104 and 76. For the firstsemi-finished condition “>” (the leftmost one), the secret parameter“89” is associated with, by the processing unit 104, and then the secretcondition “>89” is formed, wherein “>89” refers to “lager than 89”. Forthe second semi-finished condition “(,)”, the secret parameter “12” and“42” are associated with, by the processing unit 104, and then thesecret condition “(12,42)” is formed, wherein “(12,42)” refers to “lagerthan 12 and less than 42”. For the fifth semi-finished condition “˜[,)”,the secret parameter “57” and “91” are associated with, by theprocessing unit 104, and then the secret condition “˜[57,91)” is formed,wherein “˜[57,91)” refers to “less than 57 or, larger or equal to 91”.Other secret conditions are formed in the same way.

Noted that, although the secrets parameters in the example are integers,it is possible that the secret parameters are real numbers in practice.In some embodiments, a single semi-condition can be associated with morethan two secret parameters. For example, for a semi-finished condition“˜[,], ˜[,]” which refers to “neither within a first range nor within asecond range””, the processing unit may associate four secretparameters, for example, 10, 20, 30 and 40, with the semi-finishedcondition to form a secret condition “˜[10,20], ˜[30,40]” which refersto “less than 10, or larger than 20 and less than 30, or larger than40”.

In this embodiment, each secret parameter is generated randomly within arange with a minimum value and a maximum value such as [1,150] so as toefficiently represent data within specific range, such as age and bodyweight, wherein the minimum value and the maximum value may be realnumbers. However, in another embodiment, the secret parameter(s) can begenerated randomly with no bound.

In step S207, for each of the secret conditions, the processing unit 104determines whether the numerical datum satisfies the secret condition.If the numerical datum satisfies the secret condition, the processingunit 104 outputs a first character as a result element; If the numericaldatum does not satisfy the secret condition, the processing unit 104outputs a second character as the result element. In this example, thefirst character is “1”, and the second character is “0”. For the firstsecret condition “>89”, since 35 is not larger than 89, the processingunit 104 determines that the numerical datum “35” does not satisfy thesecret condition “>89”, and outputs the second character “0” as theresult element corresponding to the secret condition “>89”. For thesecond secret condition “(12,42)”, since 35 is larger than 12 and lessthan 42, the processing unit 104 determines that the numerical datum“35” satisfies the secret condition “(12,42)”, and outputs the firstcharacter “1” as the result element corresponding to the secretcondition “(12,42)”. Same procedure is applied to other secretconditions.

In step S209, the processing unit 104 concatenates the result elementbeing output corresponding to the secret conditions as an alternativerepresentation for the numerical datum. In this example, the alternativerepresentation for the numerical datum is “01111101”.

With the process illustrated above, the numerical datum “35” is“transformed” into the alternative representation “01111101” which canhide the actual information of the numerical datum from the server 90,as long as the secret conditions are not revealed to the server 90.Namely, the alternative representation can be stored into a remoteserver without revealing the confidential or private information.

In the following embodiment, the method shown in FIG. 2 is used forgenerating alternative representation which may be used as a securetrapdoor. Also referring to FIG. 4 which illustrates another example ofgenerating an alternative representation for a numerical datum accordingto the present application. In this case, the situation may be that auser intends to search for one or more desired numerical values within anumerical range among the alternative representations of numerical datastored in a remote server.

In the example shown in FIG. 4, the numerical datum is a numericalrange, that is, [20, 58] which refers to “one or more desired numericalvalues within the range of 20˜58”. For the numerical range, stepsS201˜S205 and S209 are similar to the above embodiment, but step S207 ismodified to fit the input of numerical range. Specifically, step S207further includes: outputting a third character if it is unable todetermine whether the numerical datum satisfies the secret condition,specifically, if it is not true that all desired numerical values withinthe numerical range satisfy the secret condition. For example, for thefirst secret condition “>89”, since the numerical values within therange [20,58] is all less than 89, the processing unit 104 determinesthat the numerical datum “[20,58]” does not satisfy the secret condition“>89”, and outputs the second character “0”. For the second secretcondition “(12,42)”, since not all desired numerical values within therange [20,58] are within the range of (12,42) (for example, a desirednumerical value 52 is within [20,58] but is not within (12,42), and thusthe secret condition is not satisfied), the processing unit 104 outputsthe third character, for example but not be limited to, “?”, as theresult element. Other result elements are also output in the same way,as provided in the example in FIG. 4. The third character may be one ofother characters different from the first character and the secondcharacter, or may even encoded in other readable forms. After the resultelements corresponding to all the secret conditions are output, theprocessing unit 104 concatenates each result element being output as asecure alternative representation, that is, in this example, “0?1?11?1”for the numerical datum “[20,58]”. The alternative representation“0?1?11?1” for the numerical datum “[20,58]” may be used as a securetrapdoor and uploaded to the remote server for searching desirednumerical values without leaking the actual numerical range.

Looking back to FIG. 3, where 35 is represented by “011111101”, one canreadily see that the secure alternative representation “0?1?11?1” for[20,58] can result in a matching, if “?” is interpreted as a symbol thatrepresents any character. Namely, the sequence “0?1?11?1”, when used asa secure trapdoor can represent the sequence “011111101” and thus can beused to identify the sequence “011111101”, that is used as a secureindex.

In some embodiments, each third character in the alternativerepresentation is removed from the alternative representation, if thereis any third character being output (there may be no third character,only one third character or more than one third character being outputas the result element), so that the final alternative representation isfree of the third character, such as “01111” for the example in FIG. 4.In another embodiment, each third character is excluded if there existedany third character being output as result element, when the processingunit concatenates the result elements.

Looking back to FIG. 3, where 35 is represented by “011111101”, one canreadily see that the third-character-free secure alternativerepresentation “01111” for [20,58] is a subsequence of the “011111101”for 35, thus leads to a matching. Namely, the sequence “01111” used as asecure trapdoor can also be used to identify the sequence “011111101”used as a secure index.

In some embodiments, the pair of first character and the secondcharacter may be different per secret condition. As shown in FIG. 5, thepair of first character and the second character for the left-mostsecret condition is {“A”, “B”} while the other pairs are {“C”, “D”},{“E”, “F”} and so on. In such embodiments, each secure alternativerepresentation comprises more diverse characters and looks more like arandom sequence. For example, the secure alternative representation“BCEGIKNO” is generated for 35, instead of a binary sequence, and may beused as a secure index as well.

Similarly, for such embodiments, as shown in FIG. 6, one can generate asecure alternative representation for a numerical range, e.g. [20,58],which comprises more diverse characters. That is, when generating asecure trapdoor, if we use the same secret conditions and the same pairsof first character and second character as shown in FIG. 5, a securealternative representation “B?E?IK?O” is generated for [20,58] which canbe used to identify the secure alternative representation “BCEGIKNO”. Insome embodiment, the third character is removed (or excluded during theprocessing of concatenation) if any third character being output, so thegenerated secure alternative representation is third-character-free. Forexample, in such embodiments, “BEIKO” is generated and because it is asubsequence of “BCEGIKNO”, this property leads to a matching and thethird-character-free secure alternative representation can be used as asecure trapdoor.

That is, a pair of the first character and the second charactercorresponding to one of the secret conditions is different from at leastone pair of the first character and the second character correspondingto other secret conditions except self, so that the generatedalternative representation for the numerical datum may look more like arandom sequence (rather than a binary sequence). Comparing to binarysequence, such embodiments make matching against secure indexes moreefficiently without the assistance of any third character appearing insecure trapdoors.

With the present application, numerical data can be transformed intosecure alternative representations and then be stored into a remoteserver. When a user intends to search the numerical data which stored inthe remote server, the query of a numerical range may also betransformed into a secure alternative representation used as a securetrapdoor and uploaded to the remote server for searching. Since it isdifficult for the remote server or malicious person to find the actualvalue (or numerical range) from the alternative representations, theconfidentiality of the private information of the numerical data ispreserved. As the numerical datum can be a numerical range, the presentapplication supports range queries.

While the invention has been described by way of examples and in termsof the preferred embodiment (s), it is to be understood that theinvention is not limited thereto. On the contrary, it is intended tocover various modifications and similar arrangements and procedures, andthe scope of the appended claims therefore should be accorded thebroadest interpretation so as to encompass all such modifications andsimilar arrangements and procedures.

What is claimed is:
 1. A method for generating secure alternativerepresentation for a numerical datum, being performed in a processingsystem comprising a processing unit coupled to a storage unit,comprising: receiving, by the processing system, the numerical datum;providing, by the processing system, a plurality of semi-finishedconditions; associating, by the processing system, each of thesemi-finished conditions with one or more secret parameters to form aplurality of secret conditions; for each of the secret conditions:determining, by the processing system, whether the numerical datumsatisfies the secret condition; outputting, by the processing system, afirst character as a result element if the numerical datum satisfies thesecret condition; and outputting, by the processing system, a secondcharacter as the result element if the numerical datum does not satisfythe secret condition; and concatenating, by the processing system, saidresult element being output corresponding to the secret conditions as analternative representation for the numerical datum.
 2. The methodaccording to claim 1, wherein the secret parameters are generatedaccording to a range with a minimum value and a maximum value.
 3. Themethod according to claim 1, wherein the secret parameters are generatedrandomly.
 4. The method according to claim 1, wherein the numericaldatum is a numerical range.
 5. The method according to claim 4, furthercomprising: outputting, by the processing system, a third character asthe result element if it is unable to determine whether the numericaldatum satisfies the secret condition.
 6. The method according to claim5, wherein during the concatenating, by the processing system, saidthird character is excluded if any third character being output.
 7. Themethod according to claim 5, further comprising: removing, by theprocessing system, said third character if there exists any thirdcharacter being output as said result element.
 8. The method accordingto claim 1, wherein a pair of the first character and the secondcharacter corresponding to one of the secret conditions is differentfrom at least one pair of the first character and the second charactercorresponding to other secret conditions except self.
 9. A computerprogram product comprising a non-transitory computer readable mediumhaving a computer readable program stored therein, wherein the computerreadable program, when executed at a processing unit of a processingsystem, causes the processing system to perform steps comprising:receiving a numerical datum; providing a plurality of semi-finishedconditions; associating each of the semi-finished conditions with one ormore secret parameters to form a plurality of secret conditions; foreach of the secret conditions: determining whether the numerical datumsatisfies the secret condition; outputting a first character as a resultelement if the numerical datum satisfies the secret condition; andoutputting a second character as the result element if the numericaldatum does not satisfy the secret condition; and concatenating saidresult element being output corresponding to the secret conditions as analternative representation for the numerical datum.
 10. The computerprogram product according to claim 9, wherein the secret parameters aregenerated according to a range with a minimum value and a maximum value.11. The computer program product according to claim 9, wherein thesecret parameters are generated randomly.
 12. The computer programproduct according to claim 9, wherein the numerical datum is a numericalrange.
 13. The computer program product according to claim 12, whereinthe computer readable program, further causes the processing system toperform steps comprising: outputting a third character as the resultelement if it is unable to determine whether the numerical datumsatisfies the secret condition.
 14. The computer program productaccording to claim 13, wherein during the concatenating, said thirdcharacter is excluded if any third character being output as said resultelement.
 15. The computer program product according to claim 13, whereinthe computer readable program, further causes the processing system toperform steps comprising: removing said third character if there existsany third character being output as said result element.
 16. Thecomputer program product according to claim 9, wherein a pair of thefirst character and the second character corresponding to one of thesecret conditions is different from at least one pair of the firstcharacter and the second character corresponding to other secretconditions except self.